Microfluidic devices are used extensively for the capture, detection, classification, or quantification of molecules, molecular complexes, viruses, cells and particulates in environmental or biological samples. These devices include one or more microchannels of sub-millimeter (mm, 1 mm=10−3 meters) cross section formed in a chip of an inert material, which direct flow of one or more fluids from one or more corresponding reservoirs to interact with each other in a reaction chamber or at a detector or both.
Microfluidics technology has recently emerged as a powerful means to manipulate fluids at a microscale and fully integrate many components and steps for complex yet very precise biochemical analyses. Some of the promising applications include the development of inexpensive diagnostic devices that can be deployed in low-resource settings especially to meet global health challenges such as the lack of facilities and personnel to carry out medical diagnostics. Current microfluidic devices fall into either droplet-based (multiphase) or continuous-flow (single phase) systems. To successfully manipulate these fluids, a number of control strategies have been proposed which often require use of pumps and valves, either integrated on chip or off-chip. Even for integrated on-chip systems, the valves are controlled by external macro-scale elements, such as computers, and require power sources; thus limiting the usefulness of microfluidic tools in resource poor and field settings.
A majority of commercially available systems depend actively on external pumps, vacuum and pressure sources, or depend passively on capillary filling. These solutions are often prohibitively expensive for field deployment. Research and development of self-contained micro-valves and micro-pumps that are integrated into the system still generate systems that fall short when it comes to reliability and commercial viability. The reasons for some of these challenges include the dominance of surface effects over volume effects at the microscale level—leading to increases in required driving pressure, large frictional forces that must be overcome and bubbles acting as capacitances which absorb the actuator-generated pressure. Such effects make it difficult to make micro-pumps that can prime themselves (e.g., see J. D. Zhan, Methods in Bioengineering, Biomicrofabrication and Biomicrofluidics). In addition, current systems are designed for single use. While fabricating the devices in a large batch may help reduce the costs, clean-room processes and material costs can quickly add to the cost and are typically not available near resource-poor deployments. Moreover, running a complex protocol often requires a very complex device design and/or highly skilled personnel to carefully run through multiple steps with a low error rate.
Complexity of current microfluidic systems (control systems, number of parts, fragility) renders them ineffective in harsh conditions and field settings, often encountered in global health and other applications.